Endesa petitioned the court on the grounds that a deal agreed between Gas Natural and Iberdrola, another leading Spanish utility, contravened EU rules on free trade. The deal would see between E7 and E9 billion worth of assets transferred to Iberdrola once the Endesa takeover was complete.

The appeal is one of several lodged by Endesa as it fights to face down the hostile Gas Natural bid of E22.6 billion. A rival offer, from German heavyweight E.ON of some E29 billion, is currently under scrutiny from Spain’s energy regulator.

The Spanish government has made it clear that it would prefer to see Gas Natural win the race for Endesa, enabling it to create a national energy champion. However, a recent decree giving the energy regulator greater powers to hinder a foreign takeover of a Spanish utility has landed the Zapatero government in hot water with the EU.

The internal markets commissioner Charlie McCreevy is apparently set to recommend that the EU Commission take legal action against the Spanish government over its handling of E.ON’s approach, Reuters reports.